Optical fiber transmission systems are becoming widely used in the transmission of signals such as data, voice and the like and, in many instances, are replacing traditional electrical systems. Many of the arrangements common to electrical systems, such as coupling, interconnection, splicing, and the like have their counterparts in optical systems but, because of the totally different characteristics of the transmission media, ie., optical fiber versus metallic wire, connectorization, splicing, and the like involve quite a different apparatus. Where, for example, it is necessary to make a great number of connections in one location, both systems may use what is referred to in the art as patch panels, which provide arrays of connector adapters for interconnection, but the interconnections themselves are generally quite different.
It is common practice in the optical connector art to terminate a length of optical fiber with a connector, an example of which is the SC type connector that is shown and described in U.S. Pat. No. 5,212,752 of Stephenson et al There are numerous types of such fiber terminating connectors, and, inasmuch as there has been little effort directed to standardization, each type of connector generally requires a different coupling arrangement to permit interconnection of two fibers, for example. The SC and ST type connectors are becoming more and more popular, and the remainder of the discussion, in the interest of simplicity, is devoted primarily to such connectors. It is to be understood that the following description of the principles and apparatus of the invention is applicable to other types of connectors as well such as, for example, the LC type. As is shown in that Stephenson et al. patent, an SC connector includes a ferrule assembly including a barrel having a collar at one end and an optical fiber terminating ferrule projecting from the barrel. The ferrule assembly is disposed in a plug frame such that an end portion of the ferrule projects from one end of the frame. The plug frame is configured to snap lock into a grip member having a locating key thereon, and the grip is inserted into one side of a slotted coupler adapter, with the locating key inserted into the slot. The grip of a corresponding SC connector is inserted into the other side of the adapter so that the ends of the ferrules abut each other to form a low insertion loss optical interconnection. In the SC connector, the ferrules are spring loaded longitudinally to insure contact between the fiber containing ferrule ends. The entire interconnect operation involves linear motion only and results in a low insertion loss, mechanically stable, protected junction between two fibers. The expenditure of time in making the interconnection is small and the operator or installer is relieved of having to perform anything other than simple linear motion in plugging the connectors into the coupling adapter.
When large numbers of such interconnections are to be made, it is common practice to use patch panels for holding an array of a large number of coupler adapters. Thus, there can literally be hundreds of such adapters, all in close proximity to each other, mounted in the panel. As long as only a single type of connector, such as the SC connector, is involved, simple adapters may be used for plugging in the connectors from each side of the patch panel. In view of the fact that there are several different types of connectors in widespread use today, it has become common practice to replace the simple adapters with buildout blocks or buildout coupling adapters. In U.S. Pat. No. 5,274,729 of King et al., there is shown a buildout coupling adapter system in a patch panel that makes possible interconnections among the several different types of connectors in any combination thereof. As can be seen in that patent, a buildout block at one side (or end) thereof is configured the same as a simple coupler adapter having a keyway for receiving, for example, an SC connector. The other end of the buildout block is formed to receive a buildout which may be configured to receive and hold, for example, an SC, an ST, or an FC connector. Thus, the patch panel may be, on one side thereof, pre-connectorized with optical fibers all of which are terminated by SC connectors, and the other side of the panel is ready to receive pre-connectorized fibers terminated by any one of the numerous connectors. Such an arrangement is more versatile and adaptable than those arrangements which are limited to a single type of pre-connectorized fiber. Such an arrangement also functions well in those installations where one side of the panel is not readily accessible. Thus, the panel can be pre-connectorized before mounting in position on the side which will be relatively inaccessible, after which it can be mounted in place, ready to receive the numerous connections thereto, regardless of connector type.
In any such arrangement, there is always the possibility of airborne contaminants or dust entering vacant apertures in the adapter as well as a potential safety hazard. Where one or more of the pre-connectorized fibers is carrying optical energy, such energy can be emitted from the end of the fiber connector and pass through the buildout block or coupling adapter to the side of the panel where connections are to be made. This optical energy can be harmful for the operator or installer and can be especially harmful to his or her eyes. This hazard is most prevalent when an active connection has to be repaired or otherwise altered by removing an existing connectorized fiber and replacing it with another. In such an instance, it might be difficult or otherwise impractical to shut off the signal transmission in that particular fiber circuit, hence, the installer is forced to deal with a light emitting junction or connection.
This hazard has been recognized and there have been efforts made, in the prior art, to provide a dust cover for the opening in the buildout block or adapter to block at least some of the light emanating from a fiber connection through the open adapter. One such arrangement comprises a door like member pivotally mounted to the end of the adapter, with a biasing spring adapted to maintain the door in its closed position, blocking the open end of the adapter. When a connection is to be made, the installer, for example, presses on a projecting ledge at the end of the door to pivot the door up against the spring bias. The door has to be held open while the connector is inserted into the adapter. Thus, the installer is forced to use both hands in making a connection. In most patch panels, the adapter or buildouts are arrayed quite close together, thereby making it awkward or difficult for the installer to open the shutter or door and hold it open without interfering with other connections. In addition, there is a moment, when the door is pivoted open, when light energy is not blocked and thus emerges from the adapter. Prior art arrangements of the spring loaded type are not, therefore, completely successful in that they require the use of two hands, and do not completely block the light during connectorization.
In U.S. Pat. No. 5,687,268 of Stephenson et al (Stephenson 6-1) incorporated herein by reference, there is shown an optical shutter for a lightguide adapter which overcomes many of the problems encountered in the prior art.
The invention disclosed in that application is an optical shutter or dust cover for use with optical fiber coupling adapters which has a front, transverse face which is sufficient to cover the opening in the adapter. The transverse portion has a pair of pivot arms extending from either side thereof which are adapted, at their distal ends, to be pivotally connected to the coupling adapter, thereby providing a pivotal mounting for the shutter. The transverse face also has a flange extending from one end thereof to permit actuation of the shutter, ie., opening or closing by means of the connector to be inserted in the adapter or after its removal from the adapter. The shutter is gravity operated, and provides the desired degree of protection; however, it depends upon gravity and friction for proper operation, and, where the adapter is mounted vertically in the patch panel, the gravity actuation is nullified and the shutter may be accidentally opened or moved from the closed position.
Another problem inherent in the adapter arrangement is that dust or other contaminants can enter the openings which receive connectors when no connectors are inserted therein. Heretofore, various types of plugs have been used to close the vacant openings, but these are easily lost or otherwise mislaid.